How to Make It
Measure the flours, butter and salt into the container of a food processor and turn on the machine for about 30 seconds to blend thoroughly. Add the sugar, shortening, egg and vanilla; process just until the dough masses together. On a lightly floured work surface, press the dough into a disk 1 inch thick, sprinkling on a little flour if the dough is sticky. Wrap in plastic and refrigerate for at least 1 hour, or until firm.
Set the dough on a lightly floured work surface and start beating it with your rolling pin, frequently rotating the dough as you gradually form a circular shape. When soft enough to roll, transfer the dough to a lightly floured 18-inch square of heavy duty foil. Working rapidly so the dough remains cold, start rolling it out into a roughly circular shape 3/16 inch thick; patch the dough in places as necessary. With a knife, trim the dough into a 12-inch round—you'll have a handful of leftover scraps to freeze for your next tart. Slide the dough onto a cookie sheet and freeze for 5 minutes.
Roll the edge of the dough up over itself to make a 3/4-inch border. Then roll the border over onto itself, making an upstanding edge. With lightly floured fingers, pinch the thick, raised edge to form a rim 3/4 inch tall and 3/16 inch thick. Make the height even all around, since the filling will leak out at any low spots. Decorate the outside of the rim by supporting the inside with your fingers as you press the outside with the tines of a table fork held vertically. Trim off any extra foil, cover the tart shell and freeze for at least 30 minutes.
Preheat the oven to 350°. Using a handheld mixer, beat the cream cheese until smooth and fluffy, then cream in the butter. Slowly beat in the cornstarch, then the sugar, sour cream, egg and vanilla.
Prepare a folded strip of foil 1 inch wide and long enough to surround the tart shell with an inch extra. Butter the foil and pin the buttered side closely around the tart. Pour in the filling. Bake on the lower shelf of the oven for about 20 minutes, or until the shell is lightly browned and crisp. The filling will puff up to the top of the shell. Remove to a rack; the filling will sink. down. Let cool thoroughly to set the crust.
Slide the tart shell onto a serving platter and remove the foil. Push the apricot jam through a sieve into a 6-cup saucepan, sir in the sugar and rum and simmer over moderate heat for 2 minutes. Brush a thin layer of the glaze inside the tart. Arrange the strawberries in a circle around the inside edge of the tart. Overlap the kiwis inside and mound the berries in the center. Brush the warm glaze over the fruit and serve.